A team of researchers found evidence that an exoplanet can form quite far from its star - twice as far as the distance from Pluto to the Sun. The formation of a planet remotely from a small parent star is slightly at odds with the widespread theory of planet formation. The recently discovered planet in the constellation Hydra literally refuted the popular theory with its existence. On the other hand, it’s not the fact that it does exist - misses do happen.
As a common scenario suggests, the planet is usually formed over tens of millions of years as a result of the slow accretion of dust, stones and gas. This process most easily proceeds close to the central star. Even in the case of a disk instability scenario in which a planet collapses rapidly, it is not clear how a planet with such a small mass could form. Astrophysicist Alan Boss of the Carnegie Institute, working with a model of unstable disks, reported the following:
“If the mass of this supposed planet is really as small as we think, this is a real puzzle. The theory says that a planet cannot exist. ”
The planet is located inside a dusty gas disk near the small red dwarf TW Hydrae, whose mass is only 55% of the mass of the Sun. This discovery complements the rapidly growing list of the diversity of planetary systems in the Milky Way - every six months new potentialities for the development of exoplanets are clarified. So, this dusty protoplanetary disk lies very close to us, only 176 light-years away in the constellation Hydra.
Astronomers made observations using the Hubble Space Telescope over a wide range of wavelengths from visible to near infrared and modeled the color and structure of the disk in a way that they had not done before. Scientists have discovered a shortage of material in the disk, or a partial gap, in about 80 astronomical units (AU). 1 a.u. Is the distance from the earth to the sun. Their model showed that the recess is approximately 20 AU wide, which is slightly wider than necessary to open space for the planet and the existence of the planet in 6-28 earth masses. This property is obvious at all wavelengths, it is structural and does not differ in general. The team decided that this evidence was sufficient to form a planet that triggered the gap.
“TW Hydrae is 5–10 million years old and appears to be at the finish line of the planet’s formation before its disk is scattered,” says Alicia Weinberger, co-author of the work. - “It is enough to unexpectedly find a planet in 5-10% of the mass of Jupiter, which is formed so far. According to all the principles of planet formation, it is very difficult to find a planet with a low mass far from a star with a low mass. "
The purpose of these observations was to understand not only whether the planets actually formed, but also what conditions can lead to the formation of planets, and what chemical components will affect this process. A model from Hannah Young-Condell, a former Carnegie researcher, showed that the disk was brighter than expected, suggesting very fine dust particles raised higher than usual on average. This is surprising, since observations from radio telescopes previously showed that the disk contains dust that collects in pebbles.
Weinberger modeled the observations so that large grains of ice water could be detected in the surface layer of the disk. They were not visible, which suggested that they had grown and sank in the middle part of the disk, where they became the future storage of the planet’s water.
Lead author of the study, John Debs of the Institute of Space Science and Telescopy, noted:
“As a rule, stones are needed to form a planet. Therefore, if there is a planet in the gap [disk] and there is no dust larger than a grain of sand, there is a problem for the traditional model of planet formation. ”
The article is based on materials .
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